Illuminated dial instrument



Feb. 1957 R. A. TINICH 2,782,294

ILLUMINATED DIAL INSTRUMENT Filed Sept; 22, 1954 INVENTOR ATTORNEY ILLUMINATED DIAL INSTRUMENT Robert A. Tinich, Chicago, Ill., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application September 22, 1954, Serial No. 457,622

1 Claim. (Cl. 240-21) This invention relates to dial instruments and more particularly to instruments such as gauges employing illuminated dials.

It is desirable that instrument dials for many uses and which may be employed on vehicles or on locomotives should be so constructed as to be easily read regardless of exterior lighting conditions. Heretofore, various expedients have been utilized in attempting properly to illuminate the dials without producing a glare or leakage of light which would in any way interfere with the reading or observance of the instrument. It is also desirable that the light be diflused uniformly over the dial and that the cost or" construction be low.

An object of the present invention is to provide an instrument with improved and well diflused dial illumination.

A feature of the present invention is a transparent window with a peripheral rough edge and a source of light so placed as to be diffused by that edge.

Another feature of the invention is to provide a dial instrument with a transparent window in combination with spaced light sources for projecting light into the edge of the window and a coating on the margin of the window away from the dial whereby the light rays may be deflected from the coating to the dial.

In the drawings:

Fig. l is a view in front elevation of an instrument panel in which gauges embodying the present invention are installed;

Fig. 2 is a sectional view through a similar gauge as enclosed in a single metal case; and

Fig. 3 is a sectional view taken along the line 33 of Fig. 2 and drawn to an enlarged scale.

In Fig. 1 an instrument panel is disclosed and is of the type adapted to support a multiplicity of instruments and devices. Two instruments 12 and 14 of similar construction are shown mounted in spaced relation on the panel. Each of these instruments is provided with a conventional dial 16 or 18 and a pointer 20 or 22. Metal casings 24 and 26 are supported on the panel 10 in a conventional manner and transparent window members 28 and 30, respectively, are provided to protect the pointers and dials. The casing 24 is slotted as at 32 and 34 and the casing 26 has slots 36 and 38. These slots extend along the edges of the windows and are limited in length and each of them is approximately, but not necessarily, of the same width as the transparent window with which it is associated. Bezels 40 and 42 are utilized to-retain the windows in their positions.

Electric light bulbs 44, 46 and 48 are so arranged and supported behind the panel 10 that light rays from them will enter the windows 28 and 30 through the edges of the latter and by way of the slots provided in the respective casings. Fig. 1 shows dash lines indicating the i United States Patent ice path of the rays into the windows assuming that they travel only in straight lines. It will be seen that substantial and opposed portions of the peripheral edge of each window will be subjected to the direct light rays emanating from at least one source of light.

In order to improve the illumination, the edges of each of the windows is roughened or rough cut so that the direct light rays are diffused and deflected. This diffusion occurs as the rays enter a given window edge and also as they reflect from the opposite edge of that window and within the Window material.

Fig. 1 depicts dial windows each of which has a marginal portion 28A or 30A covered with a ceramic coating or paint to increase deflection of light rays into each instrument and against its dial. This paint coating is better illustrated in the modified form of the invention shown in Figs. 2 and 3.

In Fig. 2 a single instrument is employed and it comprises a metal casing 50 having flanges 52 and 54 by means of which the instrument is supported. A light bulb 56 is supported by means, not shown, at one side of the instrument and the rays thereof project through a slot 58 in the casing. A similar light bulb 60 is supported on the other side of the instrument and light rays thereof are directed through a slot 62 in the casing. The distribution of the straight-line light rays into a transparent window 64 is similar to that shown in Fig. l. A graduated dial 66 and a suitable pointer 68 are conventionally arranged within the casing 50 but as is the case in the instrument structures of Fig. l, the peripheral edge 67 of the Window is rough cut to increase the light diffusion. The casing 50 has an opening 69 in its front side through which the dial may be observed. A bezel 70 is made integral with the body of the casing and aids in retaining the window 64 tightly in position. The rough cut edge 67 and also the front marginal portion of the window are painted as at 72 and 74 for the purposes of reflecting light as will further appear. This paint is omitted at the areas registering with the slots 58 and 62. A cork gasket 76 is assembled in the casing 50 snugly to hold the window in position and it is backed up by an annular element not disclosed.

From the above description of the construction, it will be seen that light entering the casing slots of any of the instruments penetrates the window by way of edge portions thereof and is diffused by the rough edges and reflected by the painted surfaces on the window. Because of this diflusion and reflection, light is directed into the instrument from the window and uniformly and nonglaringly illuminates the dial.

It is preferred that two light sources be employed for each instrument in the manner shown in the drawings in order that a maximum degree of uniformity be achieved insofar as dial illumination for readability is concerned. The paint on the forward margin of each window intensifies the light reflected to the corresponding dial but in some cases light reflected from the rough window edge may be adequate and the marginal paint coating may be omitted.

I claim:

An instrument comprising a casing having a circular window of transparent substance and a dial protected by said window, means positioned to project light from at least two directions into spaced edge portions of said window, said casing enclosing said instrument and window and having slots in registry with said edge portions, the peripheral edge surface of said transparent substance of said window being rough to diffuse light, the said edge surface and the forwardly facing marginal portion of said window substance being coated with a ceramic paint for' light reflection except at said edge portions, a resilient gasket contacting the rearwardly directed marginal portion of said Window substance, and the arrangement of the dial being such that light rays originating at said means and reflected from the said coating at the window edge and margin are uniformly directed to said dial.

References Cited in the file of this patent UNITED STATES PATENTS Atkinson July 6, 1937 Carter May 28, 1940 Kollsman May 28, 1940 Triplett Sept. 10, 1940 Rylsky Dec. 31, 1946 

